After illumination with white, linearly polarized light (WLPL), cyclodextrin glycosyltransferase produced mixture of alpha-, beta-, and gamma-cyclodextrins (CD) with higher overall yield than did that enzyme when nonilluminated. The illumination also influenced the ratio of those CD and that effect depended on concentration of enzyme and illumination time. At a high enzyme concentration (0.64 U/cm(3)), regardless the illumination time, formation of beta-CD predominated. The highest yield of beta-CD was afforded after 1 h illumination and 2 h illumination led to a significant increase in the yield of gamma-CD. Three-month storage of enzyme illuminated with WLPL did not reduce its enhanced activity.